The best way for golfers to improve when they do not have time to practice is to make the most out of the time they do have. Spend 60% of your time on shots inside of 75 yards. Most amateurs gain most of their strokes near the green. When you are on the range imagine playing a hole. Hit your drive, then imagine hitting an iron into the first green, and then repeat. This way you are not just beating balls, you are adding some purpose to your session. Next, play more golf!